1. Field of the Invention
The present invention relates to an ink-jet element substrate, an ink-jet printing head and an ink-jet printing apparatus applicable as an output terminal of a copy machine, facsimile machine, word processor, a host computer and the like.
2. Description of the Related Art
An ink-jet printing apparatus has been widely used in modern business office and other clerical work section required silence, as non-impact printing apparatus. For various advantages, such as capability of high density and high speed printing, relatively easy maintenance and possibility to be maintenance free, development and improvement have been progressed for the ink-jet printing apparatus.
Among such ink-jet printing apparatus, the ink-jet printing apparatus disclosed in Japanese Patent Application Laid-open No. 59936/1979, for example, has been strongly desired to be realized for capability of high density printing and high speed printing for its structural feature and for quite easiness of designing and manufacturing of so-called full-line printing head extending overall width direction of a printing medium.
However, even in such ink-jet printing apparatus, for realizing full-line printing with high density, there has been arisen various unsolved problems in design structure of the printing head and in productivity and manufacturing ability directly associated with printing precision, certainty in printing, durability and the like.
As measures for solving such problems, Japanese Patent Application Laid-Open Nos. 72867/1982 and 72868/1982 disclose an ink-jet printing apparatus having a structure, in which the ink-jet printing head is integrated at high density for achieving high density and high speed printing, for example.
On the other hand, as the ink-jet printing head, there has been proposed a multi-value output color ink-jet printing head, in which a plurality of heating elements are disposed in an ink passages forming nozzles for ink ejection, as disclosed in Japanese Patent Application Publication No. 48585/1987, for example. The disclosed printing head has n in number of heating element within one ink passage. Each of the heating elements are independently connected to driver so as to be driven independently of the other. Sizes of respective heating elements are differentiated to each other so as to differentiate heat generating amounts thereof. Accordingly, the printing dots upon printing with the n in number of heating elements are differentiated in size. Thus, {nCnxe2x88x921+nCnxe2x88x922+ . . . +nC2+nC1+1} different printing dots can be formed. Namely, {nCnxe2x88x921+nCnxe2x88x922+ . . . +nC2+nC1+1} levels of gradation can be obtained. Such element construction will be hereinafter referred to as xe2x80x9cmulti-value heaterxe2x80x9d.
However, in the conventional construction, for all of n in number of heating elements provided for one nozzle, driving transistors corresponding to respective heating elements in one-by-one basis are required. Namely, in comparison with the nozzle density, n times greater element density is required for the transistors. In general, as the driving transistor, bipolar transistor and N-MOS transistor are employed. The element density in the nozzle direction is about 70 xcexcm. For example, when the printing density is 360 dpi (dot/inch), about (70/n) xcexcm of element density is required, and when the printing density is 720 dpi, about (35/n) xcexcm of element density is required. In order to increase the element density, some measure, such as n stage structure of the driving transistor (circuit), becomes necessary. In such case, wiring becomes complicate and the size of the head substrate becomes large.
It is an object of the present invention to provide an ink-jet element substrate, an ink-jet head and an ink-jet printing apparatus which employ multi-value heater capable of achieving high gradation levels, can simplify circuit construction and permits down-sizing.
In a first aspect of the present invention, there is provided a substrate for an ink-jet element of an ink-jet printing head ejecting an ink through a plurality of ejection openings, comprising:
a plurality of heating elements provided for each. of the plurality of ejection openings and generating a thermal energy for ejecting the ink;
a data holding circuit for holding an image data for driving the heat generating elements, by holding the image data in the number of bits corresponding to the number of the ejection openings;
a driving circuit capable of driving each of the heating elements on the basis of the image data; and
a selection circuit for selecting at least one of the plurality of heating elements provided corresponding to each of the ejection openings for driving.
In a second aspect of the present invention, there is provided an ink-jet printing head for ejecting an ink through a plurality of ejection openings, the ink-jet printing head comprising:
a plurality of passages respectively communicated with respective of the ejection openings, and a substrate for an ink-jet element;
the substrate for an ink-jet element comprising:
a plurality of heating elements provided for each of the plurality of ejection openings and generating a thermal energy for ejecting the ink;
a data holding circuit for holding an image data for driving the heat generating elements, by holding the image data in the number of bits corresponding to the number of ejection openings;
a driving circuit capable of driving each of the heating elements on the basis of the image data; and
a selection circuit for selecting at least one of the plurality of heating elements provided corresponding to each of the ejection openings for driving.
In a third aspect of the present invention, there is provided an ink-jet printing apparatus using an ink-jet printing head capable of ejecting an ink through a plurality of ejection openings for printing an image on a printing medium, the ink-jet printing apparatus comprising:
means for relatively moving the printing head and the printing medium;
the ink-jet printing head including a plurality of passages respectively communicated with respective of the ejection opening, and a substrate for an ink-jet element;
the substrate for an ink-jet element comprising:
a plurality of heating elements provided for each of the plurality of ejection openings and generating a thermal energy for ejecting the ink;
a data holding circuit for holding an image data for driving the heat generating elements, by holding the image data in the number of bits corresponding to the number of the ejection openings;
a driving circuit capable of driving each of the heating elements on the basis of the image data; and
a selection circuit for selecting at least one of the plurality of heating elements provided corresponding to each of the ejection openings for driving.
The present invention includes a plurality of heating elements for each of ink ejection openings and can obtain high gradation expression ability by selecting these for driving. Also, by providing wiring for a plurality of heating elements in common circuit construction can be simplified and downsizing of the head can be achieved.
On the other hand, by enabling selective operation of the heating element, ink ejection amount adapted to printing density can certainly obtained.